For our project Keyman for Mac, we recently updated to Xcode 10.1 on macOS Mojave (10.14.1). Since then, we have found that building the project with xcodebuild hangs, and digging deeper found that Fabric's upload-symbols tool is hanging. Enabling debug logging in upload-symbols with the -d parameter shows it hanging after the following log entry:

I tried replicating the (somewhat huge) list of environment variables that Xcode provides the script (captured with printenv in an edited version of the project), and upload-symbols still ran fine from Terminal.